Although stuttering is the impairment, sometimes severe, of verbal expression, its frequent association with strong emotional reactions, such as anxiety, amplifies and multiplies the negative consequences of not being able to "talk right." It drives the person who stutters to frequent avoidance of speaking, resulting in limited interpersonal communication and problems in social and emotional adjustment, as well as difficulties in school and academic achievement. In general, the individual's potential is compromised.
Recent research by Gordon Blood and his associates at Penn State University has shown that adolescents who stutter are four times more likely to experience bullying than their peers who do not stutter, and Rodney Gable at Bowling Green State University reported growing evidence that stuttering negatively affects career opportunities for young adults. Thus, both the immediate disorder and its consequences can be quite serious. Scott Yaruss, at the University of Pittsburgh, with Robert Quesal, at Western Illinois University, have expanded on the various aspects of stuttering in conjunction with recent definitions by the World Health Organization.
Changes in Perspective
During the past 80 years, as sizeable, organized scientific interest in stuttering developed and grew, there were several cycles of change in its theory, research, and clinical aspects, reflecting vibrant activity of scholars and clinicians. Particularly noticeable changes have occurred during the past 30 years or so. Among them:
- Conceptions regarding etiology have shifted from learning perspectives to those of multiple etiologies grounded in genetics.
- In epidemiology, the concept of uniformity in onset, development, and classification, has shifted to emphasize diversity.
- Regarding the neurophysiology underlying stuttering, attention has shifted from peripheral neuromuscular characteristics of speech to central processes of language formulation and speech perception, planning, and execution (although not to the exclusion of the first).
- In the clinical domain, treatment for adults has shifted from stuttering modification to fluency enhancement. For preschool age children, the dominant approach of indirect modes (e.g., modifying children's home environment) shifted to include direct speech modification.
- In research, there has been a considerable shift from focus on adults to young children who stutter.
Prevalence and Onset
Although literature and other media depict stuttered speech as conveying hesitation or fear in adults, stuttering is actually much more common in young children. First, it almost always begins in early childhood. At the University of Illinois Stuttering Research Program, data from hundreds of preschool age children have shown that in 68% onset occurred by 36 months of age with 95% by 48 months of age. This is considerably earlier than what was previously believed.
No wonder that the close proximity between stuttering onset and the period of fast expansion in children's language invites speculation as to possible etiological stuttering-linguistic connections. For example, Nan Bernstein Ratner at the University of Maryland has hypothesized that asynchronies or perturbations in particular skill or ability areas central to speech-language formulation and production render children particularly vulnerable to fluency failure. Second, whereas many clinicians know that the prevalence of stuttering (number who stutter at a given time) in the general population is 1%, the magnitude of the problem is much larger among young children. Not only the incidence (the number who ever experience stuttering) is approximately 5% among children under age 5 or 6, but the prevalence (those who stutter at any given time) is much higher than in adults. Our findings from a large direct survey of preschoolers revealed prevalence of nearly 2.5%, more than twice that of the population at large.
These statistics have important implications in questioning the notion that stuttering is a "small problem" in terms of its occurrence. Therefore, speech-language pathologists working with preschool children should expect to encounter many more stuttering cases than clinicians working with older children or adults. Hence, we urge updated knowledge about diagnosis, prognosis, counseling, and treatment methods, especially for this group of professionals.
Interestingly, and contrary to past beliefs that stuttering is more common in African American children, Adele Proctor from our team found that the prevalence of stuttering among more than 2,200 African American preschool children we screened was no different than that for European American children.
Our studies have put to rest old myths about early stuttering. One fascinating aspect is its onset. The beginning of stuttering is different from that of the most common childhood communication disorders. Typically, children who speak normally do not wake up one morning with a phonological or language disorder. Nothing new occurs and there is no loss of an already established normal function. Instead, parents or others gradually realize that normal acquisition of speech and language has failed to occur.
In contrast, the onset of stuttering is characterized by definite changes and loss of an existing normal function: fluency. Both child and parents may react quite strongly to the appearance of unusual speech characteristics. We found that although it is true that in some cases stuttering onset is gradual, characterized by "simple" repetitions and lack of clear awareness on the part of the child, there is great diversity in the manner of onset. For example, nearly 40% of the children had sudden onsets (within a day or two). Currently, we are investigating the possibility that the manner of onset (e.g., sudden vs. gradual) is a significant prognostic differentiating factor.
Also, from the very beginning, symptomatology can be quite rich, much more than easy repetitions. For some children it includes multiple repetitions per instance, sound prolongations, silent blocks, excess tension and movement, respiratory abnormality, and other secondary characteristics. Furthermore, our data suggest that some preschool children are aware of the stuttering from a very early age, and that awareness grows rapidly after age 4. In short, what has been regarded as an "advanced" form of stuttering can often be observed very close to the time of onset.
Similarly, and contrary to past information, instead of the expected high concentration of children having mild stuttering at onset, the distribution leans the other way. Most parents rated the initial stuttering as moderate (45%) or severe (20%); only a minority of 35% thought it was mild. Clinicians' ratings indicate an even larger proportion for the moderate-severe categories.
Another important contribution is our carefully assembled normative disfluency data, derived for each age bracket within the preschool range. These provide clinicians with useful means of differentiating incipient stuttering from normal disfluency. Again, contrary to past beliefs that there are large, confusing overlaps between these two categories of speech, the new data show that, when relevant measures are applied (certain types of disfluency combined with length), early stuttering is very different from normal disfluency. Such differences are also backed up with data obtained from various acoustical analyses of disfluent speech. Whereas in the 1950s Wendell Johnson insisted that stuttering begins when parents react negatively to normal disfluency, we have sound evidence to support a conclusion that parents actually are reacting to abnormal disfluency. That is, it is quite unlikely that stuttering is caused by environmental reactions to the child. As knowledge of the role of genetics grows, environmental agents are now viewed primarily as forces that shape the onset and development of the stuttering. Similarly, although learning does not appear to be the ultimate, or sufficient, cause of the disorder, stuttering treatments reflecting learning models have been shown to be rather promising.
All these findings have important clinical implications. In particular, we question traditional views that intervention for early childhood stuttering should be only indirect (e.g., parent counseling, or, perhaps, play therapy), aimed at preventing children from becoming aware of their stuttering, as well as preventing normal disfluency from developing into "real stuttering." As stated, the data suggest that speech is abnormal from the very beginning. The presence of complex speech and physical symptomatology and the evidence for some awareness would seem to justify direct treatment methods. Indeed, several modern programs-such as those developed by Glyndon and Jeanna Riley of California State University, Fullerton; Mark Onslow of the University of Sydney, and his associates; and Janis Ingham of the University of California, Santa Barbara-although representing different approaches, all apply direct speech treatment to preschool children who stutter.
Another important outcome from the Illinois Stuttering Research Program was the reversal of the traditional concept that stuttering typically develops in an ascending manner, constantly increasing in complexity and severity. Our findings, backed by multiple data sources, clearly demonstrate that in the majority of cases stuttering follows a declining course, leading to complete recovery in at least 75% of the children (although we think that the actual percentage is higher).
Furthermore, it is now possible to estimate the remaining chance of recovery at increasing time intervals past onset. For example, after three years of stuttering the chance of natural recovery diminishes to only about 15%. Whereas we, as well as several previous investigators, are inclined to view this phenomenon as natural (spontaneous) recovery, a few have argued that the observed recovery is more likely the result of environmental factors, such as parents' active correction of the child's stuttering (negating the traditional view that calling the child's attention to his/her stuttering will make it worse). We must point out, however, that the use of evidence-based treatment may result in improvement and periods of remission at any age. In any event, the divergent developmental paths-persistency and recovery-pose exciting differential diagnosis and prognostic challenges.
Inasmuch as it would become possible to establish strong criteria for early prediction of chances for recovery or persistency, therapeutic decisions should be greatly enhanced. Children with high risk could be assigned first priority for early intervention. For those with high chances for recovery, we believe that intervention could be postponed, at least for a while, as long as the case is monitored and the child is not showing negative reactions to the stuttering. Not surprisingly, this issue has been the center of heated controversy. Some clinicians are adamant in insisting on immediate intervention for every child who begins stuttering. In our view, science will increase justification for, and economic factors will dictate, a responsible triage strategy. Progress has been made toward this end. Among factors we found to increase the risk for persistent stuttering in very young children are gender (boys are at higher risk), the specific pattern of familial history of stuttering (tendencies for persistency among relatives), disfluency patterns (a stable frequency curve of certain types of disfluency over a period of several months), and, of course, time elapsed from onset. Other factors, including head and neck movement, phonological skills, types of disfluency, and stuttering severity, should be considered but they are secondary in importance.
Although a very promising start has been made, the ability to make early predictions with a high level of accuracy has remained a central challenge. An important obstacle for prognosis has been the traditional conceptualization of stuttering as a rather monolithic disorder. That is, in spite of extreme variability in stuttering, as well as in individuals who stutter, by and large stuttering has been handled in the research and clinical arenas as a unitary disorder. Various classifications of stuttering, or of people who stutter, have been offered but none has received wide recognition either in clinical practice or in selecting participants for scientific studies.
Research in Progress
Unfortunately, little research has been conducted in this domain. Therefore, currently we are engaged in a multi-site project funded by the National Institute on Deafness and Other Communication Disorders of the National Institutes of Health (NIDCD/NIH), with the broad objectives of studying the pathognomony of stuttering, pursuing the delineation of subtypes in general but with particular reference to persistent (chronic) and recovered (transient) stuttering.
Toward this end, our team of 10 scholars from several universities is attempting to identify subtypes of stuttering by integrating detailed data of candidate risk and/or ameliorating factors from four domains: epidemiology and genetic, motor, linguistic, and personality, looking simultaneously at the four domains in each of three groups of participants: preschool children, school age children, and adults. The project is quite unique in the study of the disorder of stuttering, bringing together state-of-the art science in a range of areas of inquiry necessary for full understanding of the nature, character, pathways, and outcome of early childhood stuttering. It reflects a transition from a view of stuttering as a homogeneous disorder that progresses in a linear fashion to that of subtype differentiation.
One of the most exciting as well as promising research lines most likely to contribute to the understanding of stuttering and its diversity is genetics. Only a few years ago our team employed statistical methods applied to data on familial distribution of the disorder and reported strong evidence for genetic components to stuttering in general, as well as for its persistent and recovered forms. Very recently, however, we have completed, under the leadership of Nancy Cox, an international study of biological genetics where full genome analyses of hundreds of blood samples obtained from the United States, Israel, and Sweden, were performed. Although it is a bit too early to provide specific findings of our linkage analysis study, they seem to be bringing us closer to knowing where genes underlying stuttering might be located in the genome. Of course, there is still much work to be done. Even after researchers discover how stuttering is transmitted, what precisely is transmitted and what environmental factors are critical in influencing it may remain unknown for a long time.
Although various possibilities as to what is being genetically transmitted remain open, there are good reasons to speculate that current and near-future research will lead us closer to linking genes to auditory processing, central language/speech planning, and motoric aspects to stuttering. A number of researchers, including Hans Bosshardt of Ruhr University in Germany, Edward Conture of Vanderbilt University, and Ruth Watkins of our University of Illinois team, have been investigating interferences in cognitive, linguistic, and phonological processing in both children and adults who stutter. Ann Smith, of Purdue University, has been looking at the motor-language links.
Another exciting line of research, brain imaging, pursued in several laboratories, holds great promise in discovering brain structures and processes associated with speech and language and the eventual coordination of neural execution that may affect stuttering. For a few examples, Anne Foundas of Tulane University has reported some structural differences in the brains of people who stutter. A variety of functional differences focusing on quite a few regions of interest in the brain have been identified by other investigators and their associates, including A. Braun of NIDCD, Luc DeNil of the University of Toronto, Roger Ingham of the University of California, Santa Barbara, and Joseph Wu of the University of California, Irvine.
One of the findings that appears quite robust is that in people who stutter, the right hemisphere as well as the left is involved in speech, as opposed to normally fluent speakers who rely more on the left hemisphere for this function. So far, however, brain imaging research in stuttering has focused on adults, making it difficult to know if the observed differences were present at the onset of stuttering or, perhaps, reflect the effect of years of stuttering. Currently, however, several members of the University of Illinois Stuttering Research Program, under the leadership of Nicoline Ambrose, have extended this line of research to children.
Much work is still ahead of us in the genetics of stuttering and brain structure and function, as well as other domains such as motor function and personality/temperament. However, it appears to us that the rate of progress has been accelerated in recent years and that the field is moving toward a stage where it will be possible to relate and meaningfully combine the information coming from all directions-for example, how kinematic aberrations of the jaw are related to genes underlying brain structures responsible for speech planning processes and coordination of execution. Such understanding should enhance differential diagnosis, prognosis, and counseling. We should then know what exactly is wrong and how to design treatment based on strong scientific evidence. A few years ago, Richard Curlee of the University of Arizona entertained the possibility that stem cell treatment might be used to fix, or replace, whatever is faulty with the speech system that causes stuttering. At the current rate of progress, we will not be surprised if his prediction comes true.
Acknowledgement: The preparation of this manuscript was supported by the National Institute of Deafness and Other Communication Disorders, Grant #R01-05210, PI: Ehud Yairi.